Black holes are supermassive collapsed stars. They are called 'black' because gravity inside the black hole is so strong that even light cannot escape.

Oh yes it can, said celebrated physicist Stephen Hawking a quarter of a century ago. Hawking's mathematical gymnastics showed that black holes could radiate light or particles — hence the eponymous 'Hawking radiation'.

End of story? Not quite, announce Maulik Parikh of the Spinoza Institute in the Netherlands and Frank Wilczek of Princeton's Institute for Advanced Study. The maths, they claim, never quite matched the 'pictorial' description of how Hawking radiation works, as glibly propounded by science writers and pub intellectuals. Now Parikh and Wilczek say their new derivation of Hawking radiation closes the gap1.

That 'pictorial' recipe for how to escape from a black hole goes something like this:

First, empty space is not empty. Quantum physics allows pairs of particles and their antiparticles to be continually created — as long as they go on to annihilate each other a short time later.